Thursday, November 29, 2012

A paper published today in Global and Planetary Change finds solar radiation at the Earth surface in Spain "shows a significant increase over the 1985-2010 period" of "+3.9 Wm-2 per decade." By way of comparison, the alleged forcing from increased CO2 during the same period was only 0.11 Wm-2 at the Earth surface per decade. The authors attribute the large increase in solar radiation to a "decrease in clouds and/or aerosols." Several other papers have shown a decrease in cloudiness since the 1980's could alone account for all global warming observed since the ice age scare of the 1970's.

The math:IPCC formula for alleged CO2 forcing at the top of the atmosphere based on CO2 levels from 1985 to 2010: 5.35ln[389.78/346.04] = 0.64 Wm-2Alleged CO2 forcing per decade = 10*.64/15 = 0.41 Wm-2Alleged CO2 forcing at the Earth surface per decade = 0.41/3.7 = .11 Wm-2

There is a growing interest in the study of decadal variations in surface solar radiation during the last decades, although the analyses of long-term time series in some areas with major gaps in observations, such as in Spain, is still pending. This work describes for the first time the development of a new dataset of surface solar radiation in Spain based on the longest series with records of global solar radiation (G), most of them starting in the early 1980s. Additional records of diffuse solar radiation (D), which is a component of G much less studied due to the general scarcity of long-term series, are available for some of these series. Particular emphasis is placed upon the homogenization of this data set in order to ensure the reliability of the trends, which can be affected by non-natural factors such as relocations or changes of instruments. The mean annual G series over Spain shows a tendency to increase during the 1985-2010 period, with a significant linear trend of +3.9 Wm-2 per decade. Similar significant increases are observed in the mean seasonal series, with the highest rate of change during summer (+6.5 Wm-2 per decade) and secondly in autumn (+4.1 W m-2 per decade) and spring (+3.2 Wm-2 per decade). These results are in line with the widespread increase of G, also known as brightening period, reported at many worldwide observation sites. Furthermore, the annual mean D series starts without relevant variations during the second half of the 1980s, but it is disturbed by a strong increase in 1991 and 1992, which might reflect the signal of the Pinatubo volcanic eruption. Afterwards, the mean series shows a tendency to decrease up to the mid-2000s, with a significant linear trend of -2.1 Wm-2 per decade during the 1985-2010 period. All these results point towards a diminution of clouds and/or aerosols over the area.

Highlights

► We develop a new dataset of surface solar radiation records in Spain. ► The global and diffuse solar radiation series have been homogenized. ► The global solar radiation shows a significant increase over the 1985-2010 period. ► The diffuse component shows a significant decrease during the same period. ► These results point towards a recent decrease of clouds and/or aerosols.

A new paper published in The Cryosphere examines historical length changes of glaciers in W Greenland from 1800-2010 and finds "the average rate of retreat was largest in the first half of the 20th century." Data from the paper shows the average rate of retreat peaked at 25 meters per year during the 1930's and has decelerated to about half that rate over the past 70 years. Note glaciers have been generally retreating for 20,000 years since the peak of the last major ice age, and since the end of the Little Ice Age in 1850.

Rate of length change in meters per year. Retreat rates accelerated after the end of the Little Ice Age in 1850 until the 1940's and have decelerated since.

Legend from the paper: (b) Rate of length change (ma−1) averaged over 10-yr intervals in the period 1800–2010 for each of the glaciers (light coloured lines) and their average rate of length change (red).

P. W. Leclercq1, A. Weidick2, F. Paul3, T. Bolch3,4, M. Citterio2, and J. Oerlemans11IMAU, Utrecht University, Utrecht, The Netherlands2GEUS, Geological Survey of Denmark and Greenland, Copenhagen, Denmark3Department of Geography, University of Zürich-Irchel, Zürich, Switzerland4Institute for Cartography, Technische Universität Dresden, GermanyAbstract. Past glacier fluctuations provide insight into glacier dynamics, climate change, and the contribution of glaciers to sea-level rise. Here, the length fluctuations since the 19th century of 18 local glaciers in West and South Greenland are presented, extending and updating the study by Weidick (1968). The studied glaciers all showed an overall retreat with an average of 1.2 ± 0.2 km over the 20th century, indicating a general rise of the equilibrium line along the west coast of Greenland during the last century. Furthermore, the average rate of retreat was largest in the first half of the 20th century.

A new paper published in Climatic Change reconstructs droughts in NE Arizona over the past 400 years and finds the 20th century had "fewer multiyear [severe droughts] than any other century" and that "Perhaps of greatest relevance, this study suggests that severe and sustained episodes of dual-season drought, which are largely missing from the instrumental period, have occurred multiple times in the past (e.g., 1660s, 1740s, 1890s)." The paper adds to multiple others demonstrating that global warming does not increase the frequency or severity of droughts, floods, cyclones, or extreme weather.From the paper:

"the longest continuous run of seasonal drought during the modern period was 5 years, whereas the pre-modern period contained episodes of six, seven and eight consecutive-year droughts. Similarly, the 20th century, with only 9 winter and 12 summer droughts, contained fewer multiyear events than any other century. The uniqueness of the 20th century is further highlighted by the marked occurrence of protracted dual-season pluvials, rather than drought, over this period. Perhaps of greatest relevance, this study suggests that severe and sustained episodes of dual-season drought, which are largely missing from the instrumental period, have occurred multiple times in the past (e.g., 1660s, 1740s, 1890s)."

Abstract

For over a decade, the Hopi Tribe and Navajo Nation of northeastern Arizona have suffered the effects of persistent drought conditions. Severe dry spells have critically impacted natural ecosystems, water resources, and regional livelihoods including dryland farming and ranching. Drought planning and resource management efforts in the region are based largely on the instrumental climate record, which contains a limited number of severe, sustained droughts. In this study, a new network of moisture-sensitive tree-ring chronologies provides the basis for evaluating the longer-term temporal variability of precipitation in the Four Corners region. By analyzing the earlywood and latewood components within each annual tree ring, we are able to generate separate, centuries-long reconstructions of both cool- (October-April) and warm-season (July-August) precipitation. These proxy records offer new insights into seasonal drought characteristics and indicate that the instrumental record fails to adequately represent precipitation variability over the past 400 years. Through the use of two different analysis techniques, we identify multiyear and decadal-scale drought events more severe than any in the modern era. Furthermore, the reconstructions suggest that many of the historically significant droughts of the past (e.g., 17th century Puebloan drought) were not merely winter phenomena, but persisted through the summer season as well. By comparing these proxy records with historical documents, we are able to independently validate the reconstructions and better understand the socioeconomic and environmental significance of past climate anomalies on the tribal lands of northeastern Arizona.

A paper published today in Quaternary Science Reviews finds west Greenland was "2–3°C warmer than today" from 6,000 to 4,000 years ago and that "summer temperatures were warmer than present by at least 7,100 years ago." According to the authors, "the local Greenland Ice Sheet margin was most retracted behind its present position between 6,000 and 5,000 years ago." The paper corroborates ice core data from central Greenland indicating that Greenland was significantly warmer than the present several times over the past 8,000 years despite "safe" levels of CO2. This paper and many others demonstrate that alarmist claims of a 2°C "tipping point" for the Greenland ice sheet are nonsense.

Abstract

Predicting the response of the Greenland Ice Sheet to future climate change presents a major challenge to climate science. Paleoclimate data from Greenland can provide empirical constraints on past cryospheric responses to climate change, complementing insights from contemporary observations and from modeling. Here we examine sedimentary records from five lakes near Jakobshavn Isbræ in central West Greenland to investigate the timing and magnitude of major Holocene climate changes, for comparison with glacial geologic reconstructions from the region. A primary objective of this study is to constrain the timing and magnitude of maximum warmth during the early to middle Holocene positive anomaly in summer insolation. Temperature reconstructions from subfossil insect (chironomid) assemblages suggest that summer temperatures were warmer than present by at least 7.1 ka (the beginning of the North Lake record; ka = thousands of years before present), and that the warmest millennia of the Holocene occurred in the study area between 6 and 4 ka. Previous studies in the Jakobshavn region have found that the local Greenland Ice Sheet margin was most retracted behind its present position between 6 and 5 ka, and here we use chironomids to estimate that local summer temperatures were 2–3 °C warmer than present during that time of minimum ice sheet extent. As summer insolation declined through the late Holocene, summer temperatures cooled and the local ice sheet margin expanded. Gradual, insolation-driven millennial-scale temperature trends in the study area were punctuated by several abrupt climate changes, including a major transient event recorded in all five lakes between 4.3 and 3.2 ka, which overlaps in timing with abrupt climate changes previously documented around the North Atlantic region and farther afield at ∼4.2 ka.

Highlights

► This paper presents five Holocene lake records from west Greenland. ► Chironomids provide quantitative estimates of summer air temperature anomalies. ► Peak Holocene warmth occurred from 6,000 to 4,000 years ago, with temperatures 2–3° warmer than today. ► A transient climate change is recorded at all five study sites ∼4.2 ka. ► The inferred paleotemperature history agrees well with local glacial geologic records.

Wednesday, November 28, 2012

A new paper published in the European Physical Journal finds that there has been no increase in extreme weather in central Europe over the past 250 years. Furthermore, the paper finds that extreme weather decreased in the Greater Alpine Region of Europe over the past 30 years in comparison to the preceding 30 year period. The paper adds to many other peer-reviewed papers demonstrating that global warming does not increase extreme weather as claimed by climate alarmists.Reposted from the latest edition of The NIPCC Report:Climate alarmists vociferously contend that greenhouse-gas-induced global warming is responsible for creating more frequent and greater extremes of weather of all types, such as extremely hot summers and excessively dry or wet seasons. But are they correct in this contention?In an effort designed to broach this question, Bohm (2012) first states that "South Central Europe is among the spatially densest regions in terms of early instrumental climate data," citing Auer et al. (2007); and he goes on to state that this fact allows for successfully testing for homogeneity and developing "a larger number of very long instrumental climate time series at monthly resolution than elsewhere," - which he thus proceeds to do - noting that the resulting long time series subset of the greater alpine region provides a great potential for analyzing high frequency variability from the preindustrial (and mostly-naturally-forced) period to the "anthropogenic climate" of the past three decades. More specifically, he reports that "the unique length of the series in the region allowed for analyzing not less than 8 (for precipitations 7) discrete 30-year 'normal periods' from 1771-1800 to 1981-2010."As articulated by Bohm, "the overwhelming majority of seasonal and annual sub-regional variability trends is not significant." In the case of precipitation, for example, he writes that "there is a balance between small but insignificant decreases and increases of climate variability during the more than 200 years of the instrumental period," while in the case of temperature he reports that "most of the variability trends are insignificantly decreasing." And in a "special analysis" of the recent 1981-2010 period that may be considered the first "normal period" under dominant greenhouse-gas-forcing, he finds all extremes "remaining well within the range of the preceding ones under mainly natural forcing." And he notes that "in terms of insignificant deviations from the long-term mean, the recent three decades tend to be less rather than more variable [italics added]." The study's main result - in the concluding words of the Austrian researcher at the Central Institute for Meteorology and Geodynamics in Vienna - is "the clear evidence that climate variability did rather decrease than increase over the more than two centuries of the instrumental period in the Greater Alpine Region [GAR], and that the recent 30 years of more or less pure greenhouse-gas-forced anthropogenic climate were rather less than more variable than the series of the preceding 30-year normal period." Put another way, greenhouse-gas-induced warming has not led to more frequent and/or greater extremes of either precipitation or temperature in the GAR, in clear refutation of the climate-alarmist claim as to what, in their view of the subject, should have been occurring. Additional Reference Auer, I., Boehm, R., Jurkovic, A., Lipa, W., Orlik, A., Potzmann, R., Schoener, W., Ungersboeck, M., Matulla, C., Briffa, K., Jones, P., Efthymiadis, D., Brunetti, M., Nanni, T., Maugeri, M., Mercalli, L., Mestre, O., Moisselin, J.-M., Begert, M., Mueller-Westermeier, G., Kveton, V., Bochnicek, O., Stastny, P., Lapin, M., Szalai, S., Szentimrey, T., Cegnar, T., Dolinar, M., Gajic-Capka, M., Zaninovic, K. and Majstorovic, Z. 2007. HISTALP - Historical Instrumental climatological Surface Time series of the greater ALPine Region. International Journal of Climatology 27: 17-46.

The paper uses the data potential of very long and homogenized instrumental climate time series in the south central Europe for analyzing one feature which is very dominant in the climate change debate --whether anthropogenic climate warming causes or goes along with an increase of climate extremes. The monthly resolved data of the HISTALP data collection provide 58 single series for the three climate elements, air pressure, air temperature and precipitation, that start earlier than 1831 and extend back to 1760 in some cases. Trends and long-term low frequent climate evolution is only shortly touched in the paper. The main goal is the analysis of trends or changes of high frequent interannual and interseasonal variability. In other words, it is features like extremely hot summers, very cold winters, excessively dry or wet seasons which the study aims at. The methods used are based on detrended highpass series whose variance is analyzed in discrete 30-year windows moving over the entire instrumental period. The analysis of discrete subintervals relies on the unique number of 8 (for precipitation 7) such "normal periods". The second approach is based on the same subintervals though not in fixed but moving windows over the entire instrumental period. The first result of the study is the clear evidence that there has been no increase of variability during the past 250 years in the region. The second finding is similar but concentrates on the recent three decades which are of particular interest because they are the first 30 years with dominating anthropogenic greenhouse gas forcing. We can show that also this recent anthropogenic normal period shows no widening of the PDF (probability density function) compared to the preceding ones. The third finding is based on the moving window technique. It shows that interannual variability changes show a clear centennial oscillating structure for all three climate elements in the region. For the time being we have no explanation for this empirical evidence. We argue that it should not be an artifact of any remaining data problems, but of course a centennial cyclic effect based on 250 years of data only is not really well consolidated in terms of sample length. But it is at least an interesting new feature and the subject is open for scientific discussion and for further studies dealing with circulation effects, long-term memories in the oceans etc.

Tuesday, November 27, 2012

A new paper published in Quaternary International reconstructs temperatures in SW Florida and finds that summer temperatures during the Roman Warm Period [RWP] from 300 BC-550 AD were "insignificantly different from today" and that winters during the RWP were "colder than today at 150-200 AD and 250-300 AD, similar to today at 200-250 AD, 300-350 AD and 450-500 AD, and warmer than today at 500-550 AD." The paper adds to hundreds of other peer-reviewed papers demonstrating temperatures during the Medieval, Roman, Minoan, and other unnamed warming periods were as warm or warmer than today.The paper also shows that tiny variations in Total Solar Irradiance [TSI] of less than 1 W/m2 correlated with significant changes in reconstructed temperature of up to 5C. The IPCC claims that changes in TSI during the 20th century of about 1.5 W/m2 cannot account for 0.7C observed global warming, but data from this paper and others suggests otherwise. In addition, the paper shows TSI lagged by 50 years is better correlated to reconstructed temperatures, perhaps as a result of the enormous thermal inertia of the oceans.

Modern temperature shown by double arrows on left vertical axis, coldest winter temps from 8 otoliths shown by red boxes. Grey line is variation in total solar irradiance [TSI] and black line is TSI lagged 50 years.

Figure 6. Reconstructed Roman Warm Period and Vandal Minimum summers and winters in comparison with solar irradiance change. Symbols in red represent the Roman Warm Period and symbols in blue represent the Vandal Minimum. The thin line represents the variation of total solar irradiance ΔTSI (TSI value relative to the solar minimum 1365.57 Wm−2 in 1986) and the thick line represents the same profile as the thin line but with 50-year time lag (from Steinhilber et al., 2009). (B) Open circles represent coldest temperatures selected for evaluating winter temperature. Each open square represents each archaeological otolith specimen. The height of open squares represents its average winter temperature with standard error and the width of open squares represents its chronostratigraphic range. Double arrow represents the average winter temperature of modern otolith MOD2002 (from Wang et al., 2011).

Archaeological evidence suggests that southwest Florida experienced variably warmer and wetter climate during the Roman Warm Period (RWP; 300 BC-550 AD) relative to the Vandal Minimum (VM; 550-800 AD). This hypothesis was tested by reconstructing seasonal-scale climate conditions for the latter part of the RWP (1-550 AD) by using high-resolution oxygen isotope ratios (δ18O) of archaeological shells (Mercenaria campechiensis) and otoliths (Ariopsis felis). Eight shells radiocarbon-dated to 150-550 AD recorded that the RWP summers at 150-250 AD were insignificantly different from today and the RWP summers at 250-350 AD and 450-550 AD were drier relative to today. Eight otoliths indicate that the winters were variable during the RWP, colder than today at 150-200 AD and 250-300 AD, similar to today at 200-250 AD, 300-350 AD and 450-500 AD, and warmer than today at 500-550 AD. The climate reconstructions agree with archaeological observations and are partially coherent with the history of sea-level change, with a drying and cooling trend at the 95% confidence level across the RWP/VM transition. The climate transition is not only consistent with falling sea level, but also coherent with reduced solar radiation. Reduced solar radiation may have triggered a change in atmospheric circulation patterns that precipitated the observed climate transition.

From the Things More Worrisome than AGW Dept.:The true U.S. national debt including unfunded entitlement liabilities currently exceeds $86.8 trillion, more than 5 times the oft-quoted figure of $16 trillion. This works out to $278,569 per man, woman, and child residing in the USA [2011 population 311,591,917], or over $1.1 million for a typical 4 person family. The true U.S. debt liability is increasing by $8 trillion per year, which could not be funded even if the IRS took 100% of the combined annual gross income of all US corporations and persons earning more than $66,193. James Hansen's grandchildren should rightfully be frightened about the staggering liability they will inherit, not the trivial implications of alleged anthropogenic global warming.

Hiding the government's liabilities from the public makes it seem that we can tax our way out of mounting deficits. We can't.

A decade and a half ago, both of us served on President Clinton's Bipartisan Commission on Entitlement and Tax Reform, the forerunner to President Obama's recent National Commission on Fiscal Responsibility and Reform. In 1994 we predicted that, unless something was done to control runaway entitlement spending, Medicare and Social Security would eventually go bankrupt or confront severe benefit cuts.

Eighteen years later, nothing has been done. Why? The usual reason is that entitlement reform is the third rail of American politics. That explanation presupposes voter demand for entitlements at any cost, even if it means bankrupting the nation.

A better explanation is that the full extent of the problem has remained hidden from policy makers and the public because of less than transparent government financial statements. How else could responsible officials claim that Medicare and Social Security have the resources they need to fulfill their commitments for years to come?

As Washington wrestles with the roughly $600 billion "fiscal cliff" and the 2013 budget, the far greater fiscal challenge of the U.S. government's unfunded pension and health-care liabilities remains offstage. The truly important figures would appear on the federal balance sheet—if the government prepared an accurate one.

But it hasn't. For years, the government has gotten by without having to produce the kind of financial statements that are required of most significant for-profit and nonprofit enterprises. The U.S. Treasury "balance sheet" does list liabilities such as Treasury debt issued to the public, federal employee pensions, and post-retirement health benefits. But it does not include the unfunded liabilities of Medicare, Social Security and other outsized and very real obligations.

As a result, fiscal policy discussions generally focus on current-year budget deficits, the accumulated national debt, and the relationships between these two items and gross domestic product. We most often hear about the alarming $15.96 trillion national debt (more than 100% of GDP), and the 2012 budget deficit of $1.1 trillion (6.97% of GDP). As dangerous as those numbers are, they do not begin to tell the story of the federal government's true liabilities.

The actual liabilities of the federal government—including Social Security, Medicare, and federal employees' future retirement benefits—already exceed $86.8 trillion, or 550% of GDP. For the year ending Dec. 31, 2011, the annual accrued expense of Medicare and Social Security was $7 trillion. Nothing like that figure is used in calculating the deficit. In reality, the reported budget deficit is less than one-fifth of the more accurate figure.

Why haven't Americans heard about the titanic $86.8 trillion liability from these programs? One reason: The actual figures do not appear in black and white on any balance sheet. But it is possible to discover them. Included in the annual Medicare Trustees' report are separate actuarial estimates of the unfunded liability for Medicare Part A (the hospital portion), Part B (medical insurance) and Part D (prescription drug coverage).

As of the most recent Trustees' report in April, the net present value of the unfunded liability of Medicare was $42.8 trillion. The comparable balance sheet liability for Social Security is $20.5 trillion.

Were American policy makers to have the benefit of transparent financial statements prepared the way public companies must report their pension liabilities, they would see clearly the magnitude of the future borrowing that these liabilities imply. Borrowing on this scale could eclipse the capacity of global capital markets—and bankrupt not only the programs themselves but the entire federal government.

These real-world impacts will be felt when currently unfunded liabilities need to be paid. In theory, the Medicare and Social Security trust funds have at least some money to pay a portion of the bills that are coming due. In actuality, the cupboard is bare: 100% of the payroll taxes for these programs were spent in the same year they were collected.

In exchange for the payroll taxes that aren't paid out in benefits to current retirees in any given year, the trust funds got nonmarketable Treasury debt. Now, as the baby boomers' promised benefits swamp the payroll-tax collections from today's workers, the government has to swap the trust funds' nonmarketable securities for marketable Treasury debt. The Treasury will then have to sell not only this debt, but far more, in order to pay the benefits as they come due.

When combined with funding the general cash deficits, these multitrillion-dollar Treasury operations will dominate the capital markets in the years ahead, particularly given China's de-emphasis of new investment in U.S. Treasurys in favor of increasing foreign direct investment, and Japan's and Europe's own sovereign-debt challenges.

When the accrued expenses of the government's entitlement programs are counted, it becomes clear that to collect enough tax revenue just to avoid going deeper into debt would require over $8 trillion in tax collections annually. That is the total of the average annual accrued liabilities of just the two largest entitlement programs, plus the annual cash deficit.

Nothing like that $8 trillion amount is available for the IRS to target. According to the most recent tax data, all individuals filing tax returns in America and earning more than $66,193 per year have a total adjusted gross income of $5.1 trillion. In 2006, when corporate taxable income peaked before the recession, all corporations in the U.S. had total income for tax purposes of $1.6 trillion. That comes to $6.7 trillion available to tax from these individuals and corporations under existing tax laws.

In short, if the government confiscated the entire adjusted gross income of these American taxpayers, plus all of the corporate taxable income in the year before the recession, it wouldn't be nearly enough to fund the over $8 trillion per year in the growth of U.S. liabilities. Some public officials and pundits claim we can dig our way out through tax increases on upper-income earners, or even all taxpayers. In reality, that would amount to bailing out the Pacific Ocean with a teaspoon. Only by addressing these unsustainable spending commitments can the nation's debt and deficit problems be solved.

Neither the public nor policy makers will be able to fully understand and deal with these issues unless the government publishes financial statements that present the government's largest financial liabilities in accordance with well-established norms in the private sector. When the new Congress convenes in January, making the numbers clear—and establishing policies that finally address them before it is too late—should be a top order of business.

Mr. Cox, a former chairman of the House Republican Policy Committee and the Securities and Exchange Commission, is president of Bingham Consulting LLC. Mr. Archer, a former chairman of the House Ways & Means Committee, is a senior policy adviser at PricewaterhouseCoopers LLP.

A paper published today in Environmental Research Letters reconstructs climate extreme events between 1500 and 2009 from tree ring data throughout Europe and shows extreme events have been relatively less common over the past 30 years in comparison to the past 2 centuries. The data also shows the 20th century [1900-2009] had 24 years with the climate extreme index at 2 or greater vs. 27 years during the 19th century. The paper adds to several other peer-reviewed papers demonstrating that extreme weather is less common with global warming.

Blow-up of the last 230 years from the bottom graph below. Number of extreme events shown on vertical axis. The 20th century had two highly extreme years in 1948 and 1976, whereas the 19th century had three. The 20th century had 24 years with climate extreme index => 2 vs. the 19th century had 27 years with climate extreme index => 2.

Note from the paper:

"In the pre-instrumental period, spatial patterns of reconstructed growth extremes become less distinct with decreasing site replication back in time. Yet—while we refrain from making direct comparisons with early instrumental data (e.g. Bohm¨ et al 2010)—it is clear from our results that climatically driven and spatially pervasive extensive growth extremes occurred in Europe during the past centuries."

Letter

Climatic extreme events strongly affect forest growth and thus significantly influence the inter-annual terrestrial carbon balance. As we are facing an increase in frequency and intensity of climate extremes, extensive empirical archives are required to assess continental scale impacts of temperature and precipitation anomalies. Here we divide a tree-ring network of approximately 1000 sites into fifteen groups of similar high-frequency growth variability to reconstruct regional positive and negative extreme events in different parts of Europe between 1500 and 2008. Synchronized growth maxima or minima within and among regions indicate eighteen years in the pre-instrumental period and two events in the 20th century (1948, 1976) with extensive radial growth fluctuations. Comparisons with instrumental data showed that the European tree-ring network mirrors the spatial extent of temperature and precipitation extremes, but the interpretation of pre-instrumental events is challenged by lagged responses to off-growing season climate extremes. We were able to attribute growth minima in subsequent years to unfavourable August–October conditions and to mild climate during winter months associated with respiratory carbon losses. Our results emphasize the importance of carry-over effects and species-specific growth characteristics for forest productivity. Furthermore, they promote the use of regional tree-ring chronologies in research related to climate variability and terrestrial carbon sink dynamics.

Monday, November 26, 2012

The IPCC claims that a warming climate causes an increased variability of precipitation and that wet areas will become wetter and dry areas drier. However, a new paper published in Geophysical Research Letters finds on the basis of global observations from 1940-2009 that the opposite was true: precipitation variability decreased, there was no significant change in global average precipitation, and that dry areas became wetter and wet areas drier. According to the authors,

"We report a near-zero temporal trend in global mean Precipitation. Unexpectedly we found a reduction in global land Precipitation variance over space and time that was due to a redistribution, where, on average, the dry became wetter while wet became drier."

We report a reduction in Precipitation variability and explain how that arose

The reason of the reduction of Precipitation variability is dry got wetter and wet got drier

A new detection method is proposed to confirm the conclusion

Fubao Sun

Research School of Biology, Australian National University, Canberra, ACT, Australia

Australian Research Council Centre of Excellence for Climate System Science, Sydney, New South Wales, Australia

Michael L. Roderick

Research School of Biology, Australian National University, Canberra, ACT, Australia

Australian Research Council Centre of Excellence for Climate System Science, Sydney, New South Wales, Australia

Research School of Earth Sciences, Australian National University, Canberra, ACT, Australia

Graham D. Farquhar

Research School of Biology, Australian National University, Canberra, ACT, Australia

Australian Research Council Centre of Excellence for Climate System Science, Sydney, New South Wales, Australia

In our warming climate there is a general expectation that the variability of precipitation (P) will increase at daily, monthly and inter-annual timescales. Here we analyse observations of monthly P (1940–2009) over the global land surface using a new theoretical framework that can distinguish changes in global P variance between space and time. We report a near-zero temporal trend in global mean Precipitation. Unexpectedly we found a reduction in global land Precipitation variance over space and time that was due to a redistribution, where, on average, the dry became wetter while wet became drier. Changes in the P variance were not related to variations in temperature. Instead, the largest changes in P variance were generally found in regions having the largest aerosol emissions. Our results combined with recent modelling studies lead us to speculate that aerosol loading has played a key role in changing the variability of P.